Generators for producing pulses of alternating current



Jan. 6, 1959 J. H. COQUELET 2,867,798

GENERATORS FOR PRODUCING PULSES OF ALTERNATING CURRENT Filed April 25,1955 P2 M p cwvreox. flew/r5. .i 532L 25? G-A/A705 GENERATORS FORPRODUCING PULSES OF ALTERNATING CURRENT Jules Hector Coquelet, Jamioulx,Belgium, assignor to Atelirs de Constructions Electriques de Charleroi,Brussels, Belgium, a Belgian company Application April 25, 1955, SerialNo. 503,505 'Claims priority, application France May 18, 1954 3 Claims.(Cl. 340359) This invention relates to generators for producing shortpulses of alternating current, and particularly to generators of thetype in which the current is generated in a coil associated with avibrating blade in a magnetic circuit.

The vibrating blade may be fixed at one end to the magnetic circuit withthe other end of the blade left free to vibrate in a gap of the magneticcircuit. The blade preferably is held in a deflected position and thensuddenly released to vibrate freely and thus produce a pulse ofalternating current. If the blade is released by a pawl operated bylevers or other means in such a way that the blade begins to move at thesame time as the lever or other operating means, then certain drawbacksoccur. Particularly, the release of the blade is not sufliciently abruptand uniform. This results in non-uniform pulses having considerablevariations in shape and duration. In order to obviate this drawback itis important to release the blade sharply and precisely every time, andthis is one of the objects of the invention.

The foregoing object is attained according to one exemplary embodimentof the invention by maintaining the blade in a deflected condition underthe action of a springbiased lever, and then releasing the blade by asharp impact on the lever by a plunger core of an electromagnet, whichcore strikes the lever only at the end of its stroke.

Another object of the invention is to make possible a precise control ofthe amplitude of the pulse. This object is accomplished by providing theelectromagnet with an abutment screw against which the lever rests.Adjustment of the screw continuously varies the initial deflection ofthe blade and hence the amplitude of the generated current.

A further object of the invention is to generate pulses of which thefirst oscillation is of maximum amplitude so that the rise time orbuild-up time of the pulse is a minimum. This object is attained bybending the blade in its resting position so that the blade vibratesinitially with its maximum amplitude.

A still further object of the invention is to reduce or substantiallyprevent the production of transients or other irregularities of thecurrent from the current generator. Such irregularities appear to beproduced by vibrations resulting from the impact of the plunger on thelever. It has been found that these irregularities can be substantiallyprevented without appreciably reducing the sharpness of the impact onthe lever by providing suitable damping means between the lever and theplunger.

Other features and objects of the invention will become apparent fromthe following detailed description thereof and the accompanying drawingthe single figure of which illustrates a vibrating blade generatoraccording to the invention.

Referring to the drawing, there are shown only the elements essential toan understanding of the invention. A vibrating blade A is fixed at itslower end to an anchoring piece of soft iron A and is free to vibrate atits upper end. The blade is formed of a resilient magnetic material.

States Patent P2 for limiting its axial movements.

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The vibrating portion of blade A is positioned in the gap M1 of amagnetic circuit M2 of a magnet M, which may be a permanent magnet. Acurrent generating coil B is associated with the blade A so that theflux through coil B varies with the position of blade A in the gap M1.At rest, the blade A is held bent by the action of a spring R on a leverL.

The lever L has a fixed fulcrum O and is shaped so that it is necessaryonly to pivot the lever L against the pull of spring R to release thevibrating blade A. This action is produced by an electromagnet I havinga plunger core P. The core P has a cap or flange P1 and an offset Acompressible hammer U rests freely on the top of plunger P. When theelectromagnet I is energized, the core P is drawn upward into the coilI1 and strikes the lever L near the end of its stroke. At the moment ofimpact the plunger P has all the kinetic energy it has stored up duringits stroke, and in addition the attracting force of the electromagnet isthen at a maximum value. The impact of the plunger on the lever L makesit pivot and thereby permits a quick and sharp release of blade A.

When the blade A is thus released it begins to vibrate at its naturalfrequency. As a result, the intensity of the magnetic field through coilB is varied periodically and an E. M. F. is induced in this coil havinga frequency corresponding to the frequency of vibration of blade A. Theinduced E. M. F. and the generated current have an amplitude determinedby the initial deflection of blade A. To vary the deflection of blade Ait is only necessary to adjust the initial position of lever L. This isdone by means of an abutment screw E threaded on the end of the casingC. Adjustment of screw E moves lever L against spring R to adjust thedeflection of blade. A. A central opening E1 in screw E permits thepassage of the member U therethrough. The coil I1 is held in place by anadditional screw D which also is provided with a central opening forpassage of the plunger.

While it is necessary to administer a sharp and sudden impact to lever Lin order to obtain uniform pulses, such shocks tend to produceirregularities in the output current. This dilemma is resolved by thehammer or damping member U. This member may be formed ofpolycaprolactame or any suitable plastic or compressible member may beused which is capable of damping out the parasitic vibrations which giverise to the undesirable irregularities of the output current from coilB.

In teleprinter circuits of the type described in my application SerialNo. 485,490 filed February 1, 1955, short current pulses having twelvedifferent frequencies are transmitted to represent a five unit code.These current pulses can be supplied by a like number of generators ofthe type herein described, arranged so that the vibrating blades vibrateat the different desired frequencies of the currents. Each time a pulseof a particular frequency is required, a control current is impressed byone of the control circuits G1G12 on the coil of the electromagnet forthat frequency. This causes the plunger P of that electromagnet, thelever L, and the blade A to operate, and thereby produce a current incoil B of the required frequency.

end in said magnetic circuit and having its other end free to vibratenear a pole of said magnetic circuit and being able to conduct flux,means including a pivoted lever for adjustably and releasably holdingsaid blade in a predetermined bent position which is determinative ofthe maximum amplitude of the vibrations of said blade when released,means. constantly biasing the lever toward av position for bending theblade, an electromagnet having a movable plunger core which is impartedmovement when the electromagnet is energized for delivering an impact tothe lever at the end of its movement and for moving said lever away fromsaid blade in a general direction toward which the blade tends to moveinitially when released from its bent position, and means including acoil surrounding said blade for producing a current corresponding to thevibrations of said blade.

2. A current generator according to claim 1, including resilient meansfor preventing said impact from producing spurious frequencies in saidcurrent.

3. In a teleprinter system for selectively sending short successivepulses of alternating current of different frequencies, in combination,a plurality of current generators, each generator comprising a magneticcircuit, for each generator a blade of resilient magnetic materialfixedly connected at one end and having its other end free to vibratenear poles of an associated magnetic circuit, a coil in each generatormagnetically coupled to said vibrating blade, means including a singlepivoted lever for each generator for adjustably and releasably holdingthe blades individually in given bent positions which are determinativeof the maximum amplitude of the vibrations of each blade when released,for each generator an electromagnet having a movable resilient coreslug, means responsive to the energization of the electromagnet forcausing said core slug to move between a rest position and apredetermined operative position and near the end of its movement towardits operative position to strike said lever so as to cause said lever tomove away from said blade in a general direction toward which the bladetends to move initially when released from its bent position thereby toinstantaneously release said blade for vibration, means constantlybiasing the levers individually toward a position for engaging theirassociated blades and bending them and for cooperating with the holdingmeans in restoring the blades individually to their same bent positionssubsequent to the de-energization of the individual electromagnets, ateleprinter comprising control circuits for controlling the energizationof said electromagnets of said generators individually and forperiodically energizing and deenergizing them for short intervals oftime, whereby the blades of said generators vibrate at differentsubstantially constant frequencies and generate alternating currents intheir associated coils corresponding to the different frequencies ofvibration.

References Cited in the file of this patent UNITED STATES PATENTSi,234,650 Ferriter July 24, 1917 1,489,382 Brown Apr. 8, 1924 2,306,068Lewis Dec. 22, 1942 2,307,521 Lovell Jan. 5, 1943 2,533,136 Muldoon Dec.5, 1950 2,640,973 Cleaver June 2, 1953

